My off grid water pump progression, advice or thoughts?

learaviatorlearaviator Posts: 6Registered Users ✭✭
I have a 24 volt system, 12 Trojan L16 batteries. When I got the property with no solar, the house had a Grundfoss pressure pump. Water storage tank is about 5 feet above house level. Pump pulls about 10 amps AC. After I built the solar system I wanted to have a lower power usage pump and a friend who has been off grid for years recommended a 12 volt Remco 55 Aquajet-ARV. He told me to pick out two batteries in my bank and use them for the the 12 volts. Pump works amazing and keeps up with water usage and pressure perfectly, but was drawing those two batteries down significantly lower than the rest. Specific gravity was down to 1.200 on those two. I removed that pump and reinstalled the Grundfoss. After some researching I see where Remco makes a 24 volt version of this pump, still over 5 gpm, which would allow me to draw from the entire battery bank. I also researched DC to AC amperage comparisons and found a chart that showed to pull 10 amps AC required about 50 amps DC accounting for inverter loss and such. I would like to buy the Remco 24 volt pump as it pulls 10 amps DC at 60 psi, its shutoff pressure. Is my research correct? Any opinions would be greatly appreciated. 

Comments

  • mcgivormcgivor Posts: 2,211Solar Expert ✭✭✭✭✭
    edited August 6 #2
    When a center tap on a string of batteries is made, 12V in your case from 24V, the batteries supporting the 12V load will discharge at a higher rate than its series mates, the charger however will regulate according to the voltage of the entire string, the result will be the two used for 12V will never receive enough charge and if left that way will eventually become damaged beyond recovery. Remove the two and charge them independently, better yet equalize if possible, before any further damage occurs they will never recover if left in the 24V string.

    A DC -DC buck converter could be used for the 12V pump, or a 24V pump as you stated.
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  • learaviatorlearaviator Posts: 6Registered Users ✭✭
    Thank you!
  • mike95490mike95490 Posts: 7,908Solar Expert ✭✭✭✭
    Shirley, there is a 120V pump that will suit your flow and pressure needs that consumes less than 10A

    Since you are running a 24V system with L-16's in parallel, I'd consider, at the next battery replacement time, to upgrade the Inverter to a 48V system. less overall losses, fewer batteries in parallel (better balance between fewer banks). Not sure what your current comsumption is, if you can get by with 8, L-16's or if you'd have to use 16 to get the needed amp hours.  That will be a exercise in math, cheaper to by 8 L-16's every 4 years @ 60% DOD, or 16 every 6 years @ 75% DOD (with the longer life risking more chance a battery will fail from age before cycle life)  < insert your own correct numbers instead of my wild guesses>
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  • jonrjonr Posts: 1,077Solar Expert ✭✭✭✭
    You should do your calculations in watts, not amps.   Do that and also factor in run time and I suspect you will find that the DC pump isn't much different efficiency wise.   12VDC and 24VDC pumps usually have brushes which eventually fail.
  • wellbuiltwellbuilt Posts: 311Solar Expert ✭✭✭
    I use a sure flow park model RV pump with a 30 gallon  pressure tank 
     it puts out plenty of water for showers . 
     I can draw 5 gallons of water from the  pressure tank before the pump kicks in . 
     The pump draws 70/80 watts plus inverter draw . 
      I did not want to tap my battery for a 12 /24v pump .
     
    Out
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